In today's radio communications networks a number of different technologies are used, such as Long Term Evolution (LTE), LTE-Advanced, 3rd Generation Partnership Project (3GPP) Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/Enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible technologies. A radio communications network comprises radio base stations providing radio coverage over at least one respective geographical area forming a cell. User Equipments (UE) are served in the cells by the respective radio base station and are communicating with respective radio base station.
The base station, e.g. a Radio Base Station (RBS), is sometimes referred to as e.g. “eNB”, “eNodeB”, “NodeB”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also coverage area and cell size. A cell is the geographical area where radio coverage is provided by the base station installed at a base station site and may be equipped with one or more antennas. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several wireless communication technologies. The base stations communicate over the air interface operating on radio frequencies with the user equipments within range of the base stations.
In some Radio Access Networks (RANs), several base stations may be connected, e.g. by landlines or microwave, to a radio network controller, e.g. a Radio Network Controller (RNC) in Universal Mobile Telecommunications System (UMTS), and/or to each other. The radio network controller, also sometimes termed a Base Station Controller (BSC) e.g. in GSM, may supervise and coordinate various activities of the plural base stations connected thereto. GSM is an abbreviation for Global System for Mobile Communications (originally: Groupe Spécial Mobile).
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks.
UMTS is a third generation mobile communication system, which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipments. The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies.
According to 3GPP/GERAN, a user equipment has a multi-slot class, which determines the maximum transfer rate in the uplink and downlink direction. GERAN is an abbreviation for GSM EDGE Radio Access Network. EDGE is further an abbreviation for Enhanced Data rates for GSM Evolution.
In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to the mobile station. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the mobile station to the base station.
The possibility of identifying a geographical location of a user equipment in the radio communications network has enabled a large variety of commercial and non-commercial services, e.g., navigation assistance, social networking, location-aware advertising, emergency calls, etc. Different services may have different positioning accuracy requirements imposed by the positioning application. In addition, some regulatory requirements on the positioning accuracy for basic emergency services exist in some countries, e.g. 300 meters in Federal Communications Commission (FCC) Enhanced 911 in United States.
In many environments, the position may be accurately estimated by using positioning methods based on the Global Positioning System (GPS). Nowadays, networks have also often a possibility to assist user equipments in order to improve the terminal receiver sensitivity and GPS start-up performance, e.g. as Assisted-GPS (A-GPS) positioning do. GPS or A-GPS receivers, however, may not necessarily be available in all wireless terminals such as user equipments. Furthermore, GPS is known to often fail in indoor environments and urban canyons. A complementary terrestrial positioning method, called Observed Time Difference of Arrival (OTDOA), has therefore been standardized by 3GPP. In addition to OTDOA, the LTE standard also specifies methods, procedures, and signaling support for Enhanced Cell ID (E-CID) and Assisted-Global Navigation Satellite System (A-GNSS) positioning. Later, Uplink Time Difference of Arrival (UTDOA) may also be standardized for LTE. UTDOA is a real time locating technology that uses multilateration based on timing of received uplink signals. Multilateration is the process of locating an object by accurately computing the Time Difference Of Arrival (TDOA) of a signal emitted from that object to three or more receivers.
The three key network elements in an LTE positioning architecture are a Location Server (LCS) Client, an LCS target device and an LCS Server. The LCS Server is a physical or logical entity managing positioning for the LCS target device by collecting measurements and other location information, assisting the user equipment, e.g. the terminal, in measurements when necessary, and estimating the LCS target location. A LCS Client is a software and/or hardware entity that interacts with a LCS Server for the purpose of obtaining location information for one or more LCS targets, i.e. the entities being positioned. LCS Clients may be in any part of the network, e.g. in a core network node, in a radio base station or in a user equipment. LCS Clients also may or may not reside in the LCS targets themselves. An LCS Client sends a request to LCS Server to obtain location information, and LCS Server processes and serves the received requests and sends the positioning result and optionally a velocity estimate to the LCS Client. A positioning request can be originated from the terminal or the network.
Position calculation may be conducted, for example, by a positioning server, e.g. the LCS server, an Evolved Serving Mobile Location Centre (ESMLC) or a Secure User Plane Location (SUPL) Location Platform (SLP) in LTE, or by a user equipment. The former approach corresponds to the UE-assisted positioning mode, whilst the latter corresponds to the UE-based positioning mode.
Two positioning protocols operating via the radio network exist in LTE; the LTE Positioning Protocol (LPP) and LLP annex (LPPa). The LPP is a point-to-point protocol between a LCS Server and a LCS target device, used in order to position the target device. LPP can be used both in the user and control plane, and multiple LPP procedures are allowed in series and/or in parallel thereby reducing latency. LPPa is a protocol between base stations, e.g. the eNodeB, and LCS Server specified mainly for control-plane positioning procedures, but it may also assist user-plane positioning by querying eNodeBs for information and eNodeB measurements. SUPL protocol is used as a transport for LPP in the user plane. LPP also has a possibility to convey LPP extension messages inside LPP messages, e.g. currently Open Mobile Alliance (OMA) LPP extensions (LLPe) are being specified to allow e.g. for operator-specific assistance data or assistance data that cannot be provided with LPP or to support other position reporting formats or new positioning methods.
In a high-level architecture, as it is currently standardized in LTE, the LCS target is a user equipment such as a terminal, and the LCS Server is an E-SMLC or an SLP. In the figure, the control plane positioning protocols with E-SMLC as the terminating point are shown as LCS AP, LPPa, LPP, and the user plane positioning protocol is shown as SUPL and SUPL/LPP. SLP may comprise two components, SUPL Positioning Centre (SPC) and SUPL Location Centre (SLC), which may also reside in different nodes. In an example implementation, SPC has a proprietary interface with E-SMLC, and an Llp interface with SLC, and the SLC part of SLP communicates with P-GW (PDN Gateway) and External LCS Client.
Additional positioning architecture elements may also be deployed to further enhance performance of specific positioning methods. For example, deploying radio beacons is a cost-efficient solution which may significantly improve positioning performance indoors and also outdoors by allowing more accurate positioning, for example, with proximity location techniques.
To meet Location-Based Service (LBS) demands, the LTE network will deploy a range of complementing methods characterized by different performance in different environments. Depending on where the measurements are conducted and the final position is calculated, the methods can be user equipment-based, user equipment-assisted or network-based, each with own advantages. The following methods are available in the LTE standard for both the control plane and the user plane,                Cell ID (CID),        UE-assisted and network-based E-CID, including network-based Angle Of Arrival (AoA),        UE-based and UE-assisted A-GNSS (including A-GPS),        UE-assisted Observed Time Difference of Arrival (OTDOA).        
Hybrid positioning, fingerprinting positioning and adaptive E-CID (AECID) do not require additional standardization and are therefore also possible with LTE. Furthermore, there may also be UE-based versions of the methods above, e.g. UE-based GNSS (e.g. GPS) or UE-based OTDOA, etc. There may also be some alternative positioning methods such as proximity based location. UTDOA may also be standardized in a later LTE release, since it is currently under discussion in 3GPP.
Similar methods, which may have different names, also exist in other Radio Access Technologies (RATs), e.g. WCDMA or GSM.
A drawback with prior art systems is that they degrade positioning accuracy or negatively impact the measurement time.
Another drawback with the prior art systems is that measurements of different types are performed in a serial manner and thus take longer time. For a user equipment in discontinuous reception (DRX), this may also negatively impact the user equipment's power consumption.